This invention is directed to locks known as double cylinder tubular deadbolts. These devices are generally used in situations where it is possible to reach the lock from outside by breaking a window, and they require a key to be unlocked from either side.
Virtually all such locks conform to a conform to a method of installation for the cylinders. The inside and outside each have a cylinder (or composite cylinder/housing) with a flanged face and a collar or escutcheon with a bore that accepts the cylinder body and a counterbore to accept the flanged face. The outside cylinder has two blind holes drilled and tapped from the back and the inside cylinder has matching holes drilled through. The cylinders are installed by sliding each cylinder into its respective collar, placing them over the hole bored through the door, then sliding screws through the holes in the inside cylinder and threading them into the holes in the outside cylinder. When the screws are tightened the assembly can't be removed without tools, effectively preventing simple entry even if access can be gained to the inside of the door. If security is especially critical the inside cylinder may be fitted with screws theft require special tools for removal or small screw covers may be pushed into counterbores around the screw head, preventing access to the screw head without first prying out the screw cover. Removal of the screw covers invariably ruins them, so if cylinders have to be removed, as for painting, new covers must be purchased to complete the reinstallation. Furthermore, exposed screws, whether covered or not, are generally considered to detract from the appearance of installation.
The present invention solves these problems.